Devices with angularly adjustable sanding units

ABSTRACT

The invention describes devices consisting of a combination of oblique to feed direction aligned belt sanding assemblies, with drives or devices for low sanding belt speeds and/or with conventional, or modified for sanding belt oblique operation, electronic segmented sanding pad. The oblique alignment of the sanding unit can be adjusted steplessly. Its application for both oblique sanding and, when so aligned, sanding directly in the direction of feed meets the requirements of intermediate sanding between paint or varnish coats, as well as those of wood sanding.

This application is a national stage application, according to ChapterII of the Patent Cooperation Treaty.

BACKGROUND OF THE INVENTION

This invention describes previously unknown devices with obliquelyalignable belt sanding units, previously unknown design characteristicsof belt sanding units aligned obliquely, and previously unknownapplications of devices with obliquely alignable belt sanding units.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a conventional sanding unit with sanding belt 11, acontact device, here in the form of a segmented sanding pad 13 made upof single segments 12, and a series of contact rollers 14 forcontrolling the segmented sanding pad, with a feed table 15.

FIG. 2 illustrates a top/bottom unit with sanding pads 16 and 17, which,contrary to the obliquely aligned sanding unit, are alignedperpendicularly to the feed direction.

FIG. 3 illustrates a sanding unit with its axis of rotation 20 alignedobliquely to its feed direction, here equipped with a segmented sandingpad 13, which is in the same oblique alignment as the unit as a whole,as is the series of contact rollers 14 for the control of the segmentedsanding pad 13, which here is applied perpendicularly to the feeddirection. Due to this arrangement of contact rollers 14, differing fromthe oblique alignment of the segmented sanding pad 13, the distancesvary along the working width between the individual contact rollers andthe corresponding segments controlled by them. Section a is thereforeshorter than section b.

FIG. 4 illustrates the same representation of the sanding pad as FIG. 3,but with a contact roller series 14 in the same oblique alignment as thesanding assembly.

FIG. 5 shows illustrates an obliquely alignable unit with a motor 18 forrotation 22 and drive belt 19.

FIG. 6 shows illustrates a single segment 12 of a segmented sanding padwith its axis of rotation 21.

DETAILED DESCRIPTION OF THE INVENTION

The current state of technology includes top/bottom sanding systems withbelt sanding units which are aligned slightly obliquely to the feeddirection. The two pressure beams, required to establish contact betweenthe workpiece and the sanding belt, referred to as sanding pads 16 and17, are aligned at 90° to the workpiece. This 90° alignment of thesanding pad for the obliquely aligned sanding belt requires a sandingunit which affords a large amount of space, but which can guarantee astraight workpiece throughfeed even when there is an interruption to theworkpiece surface, which is unavoidable for sanding operations frombelow.

It is also known in professional circles that sanding belts obliquelyaligned to the feed direction have the advantage over those which workstraight in the feed direction, that any imperfections (e.g. sawdust,knot fallout, contamination with glue, dust, etc.) do not lie instraight lines, but rather repeat laterally along the workpiece. Theytherefore appear less serious and frequent. The oblique sanding marksthemselves are not disturbing on homogeneous workpieces or those whichare treated further after sanding (lamination, coating, etc.), thoughnaturally not on structured surfaces (e.g. grained timber). Sanding withobliquely aligned belts is therefore not common. An exception are theabove-mentioned top/bottom sanding units. And even with these theapplication is limited to MDF panels with high surface qualityrequirements. No such requirements for flawless surface quality exist.However for e.g. chip board (these are usually subsequently veneered),while veneer or solid wood, as mentioned, normally do not tolerate anysanding marks. An advantage of obliquely aligned sanders becomes evidentwith intermediate sanding between paint or varnish coats. For this todate unknown application other preconditions have had to be fulfilled:part of this invention is that previously, due to the thinner paint orvarnish coat, the obliquely aligned sanding unit was applied at lowersanding belt abrasive speeds (i.e. about 50% or less than the standardspeed for high-grade abrasion of around 20 m/s) and/or a specially thinsanding pad. The corresponding devices—e.g. RPM regulation via afrequency converter and the use of electronically controlled segmentedsanding pads are known, but not their combination or simultaneousapplication with obliquely aligned sanders.

To the contrary of industrial panel finishing (e.g. MDF panels), coatingand intermediate coat sanding is undertaken mostly in medium-sizedbusinesses. These have special requirements: mainly that the same unitshould sand wood panels (solid or veneer) and coated surfaces. While thestraight sand is the first requirement, the oblique sand option offersthe nominated advantages to surface finishing. The sanders musttherefore, as this invention describes, be adjustable. Should thesanding pad also be aligned obliquely, as in the case of segmentedsanding pads, then there must also be an automatic switchover fromstraight to oblique (and vice-versa) of the electronic segmented sandingpad segments 12 around their axis of rotation 21. Since theirapplication is controlled at infeed by means of contact rollers 14, thecontrol must also be made “obliquely alignable”. This is achieved eitherthrough the use of a segmented pressure or contact roller series 14,which rotates parallel to the sanding unit (and which aligns e.g. via aparallelogram suspension aligned in the feed direction), or in the caseof contact roller fixed position, via a regulated compensation acrossthe working width of the varying section gap between contact rollers andsegments.

1. A sanding device, comprising: a feed table defining a feed directionfor feeding a workpiece into the device; a sanding unit comprising asanding belt and a segmented sanding pad including a plurality ofrotatable sanding pad segments; and a plurality of contact rollers forcontrolling the application of the plurality of rotatable sanding padsegments; wherein the sanding unit is steplessly movable between a firstposition in perpendicular alignment with the feed direction and a secondposition in oblique alignment with the feed direction; wherein theplurality of contact rollers move in parallel with the sanding unit; andwherein the sanding pad segments remain parallel with the feed directionin both the first and second positions and positions therebetween.
 2. Asanding device in accordance with claim 1, wherein the segmented sandingpad is electronically controlled.
 3. A sanding device in accordance withclaim 1, wherein the plurality of contact rollers are selectivelymovable between a perpendicular alignment with the feed direction and anoblique alignment with the feed direction.
 4. A sanding device inaccordance with claim 1, further comprising a drive motor.
 5. A sandingdevice in accordance with claim 4, wherein RPM regulation of the drivemotor is controlled via a frequency converter and sanding at the obliquealignment is at a rate of about 10 m/s or less.
 6. A sanding device inaccordance with claim 1, wherein a path distance between each one of theplurality of sanding pad segments and each one of the correspondingplurality of contact rollers is the same when the sanding unit is inboth the perpendicular alignment and the oblique alignment with the feeddirection.
 7. A sanding device, comprising: a sanding unit comprising asanding belt and a segmented sanding pad including a plurality ofindividually rotatable sanding pad segments; and a plurality of contactrollers for controlling the application of the plurality of rotatablesanding pad segments; wherein the sanding unit is selectively movablebetween a perpendicular alignment with a feed direction for feeding aworkpiece into the device and an oblique alignment with the feeddirection; wherein the plurality of contact rollers move in parallelwith the sanding unit; wherein a path distance between each one of theplurality of sanding pad segments and each one of the correspondingplurality of contact rollers is the same when the sanding unit is inboth the perpendicular alignment and the oblique alignment with the feeddirection.
 8. A sanding device in accordance with claim 7, wherein thesanding unit and the plurality of contact rollers are steplesslymovable.
 9. A sanding device in accordance with claim 7, wherein thesegmented sanding pad is electronically controlled.
 10. A sanding devicein accordance with claim 7, wherein the plurality of contact rollers areselectively movable between a perpendicular alignment with the feeddirection and an oblique alignment with the feed direction.
 11. Asanding device in accordance with claim 7, further comprising a drivemotor and wherein RPM regulation of the drive motor is controlled via afrequency converter.
 12. A sanding device in accordance with claim 7,wherein the plurality of rotatable sanding pad segments are rotatable tomaintain them parallel to the feed direction when the sanding unit is inthe oblique alignment.